1. Field of the Invention
The present invention relates to an optical disc device that is capable of recording or reproducing data by directing a laser beam onto an optical disc, and particularly relates to an optical disc device that is capable of recording high-quality data regardless of temperature changes in the environment of use, and to a recording method for an optical disc device.
2. Description of the Related Art
In recent years, the recording speeds used in optical discs as information storage media capable of data recording have increased, for example, a CD-R (compact disc-recordable) or a CD-RW (compact disc-rewritable). With increasing recording speeds, the devices that reproduce or record data from an optical disc have recording/reproduction systems using a rotary drive system of the ZCLV (zone constant linear velocity) type or CAV (constant angular velocity) type, facilitating control of rotation. In particular, the rotary drive of an optical disc with a CAV system in which the linear density is fixed, as with a CD-R or CD-RW, the need to increase the optical disc speed may be more acute, since it is necessary to increase the linear speed with the increase in the track radius on the disc.
On the other hand, with the increasing popularity of miniature computers typified by notebook personal computers, the optical disc devices that are mounted in such devices are becoming thinner. This means that the various components are arranged more densely within the device, making it difficult to ensure sufficient space for obtaining air convection in the interior of the device to achieve cooling. Specifically, the heat generated in the drive LSI and other components on the circuit board for controlling the emission of laser light and the drive current thereof is confined within the interior of the optical disc device, and, in particular, to perform data recording, high laser power is required, causing a high temperature in the interior.
With increases in speed of optical discs, in particular in optical disc devices capable of recording data, a further increase in the power of the laser beam is required when recording. However, in semiconductor lasers such as laser diodes that are normally employed as laser beam sources, the laser output is limited. If an attempt is made to output a laser beam with more than the rated power, there is a risk of damaging the semiconductor laser itself. In addition, the laser output varies with the ambient temperature of the semiconductor laser, so a prescribed laser output is ensured by monitoring part of the laser output. The laser output is particularly reduced in a high-temperature environment, thus the drive current of the semiconductor laser must be increased.
If an attempt is made to guarantee laser output by increasing the drive current, excessive drive current may flow, damaging the semiconductor laser. It should be noted that this phenomenon is particularly severe in the case of optical disc devices which are themselves not very thick, as described above. A prior art technique for obtaining stable recording quality by optimal laser power control, taking into account the temperature dependence of laser power described above, is described in Japanese Laid-open Patent Application No. 2002-251735. Specifically, in this prior art optical disc recording device, temperature detection means is provided to detect the ambient temperature, particularly, the temperature of the substrate where the main ICs in the device are mounted. A correction means is provided that corrects the laser power from the laser diode in response to the signal from this temperature detection means.
Japanese Laid-open Patent Application No. 2001-34962 or Laid-open Patent Application No. 2000-90563 also discloses an optical disc device wherein an actuator that supports/drives an object lens is employed at the maximum limit of its capability, but to prevent burn-out of the drive coil that drives the actuator, the temperature of the drive coil is monitored using a heat transmission model of the actuator. The actuator is shut down in accordance with the results of this monitoring process if the rotational speed of the optical disc drops.
In addition, a device wherein, to lower the internal temperature of a recording media drive device at high temperature, a temperature sensor is provided in the interior of the recording media drive device. The sensor outputs a temperature signal, and the maximum rotational speed of the spindle motor for driving the optical disc is controlled in accordance with the temperature. See Japanese Laid-open Patent Application No. 2001-202689.
Further, from Japanese Laid-open Patent Application No. 2002-56558, a recording/reproduction device for a magneto-optic disc capable of recording a signal on a disc by means of a laser beam emitted from the optical head is known. In this system, the laser output of the optical head and the rotational speed of the spindle motor are controlled in accordance with the temperature obtained by providing a temperature detection element for monitoring the temperature within this device.
Japanese Laid-open Patent Application No. 2002-163854 discloses prevention of excessive rise in temperature of a component arranged in the interior of a disc device, caused by a fault or spurious operation of this device, by controlling disc rotation means in accordance with the change in temperature within the disc device.
Japanese Laid-open Patent Application No. 2002-272172 discloses detection of abnormality of a spindle motor of a disc recording device by periodically sampling the ambient temperature detected by a temperature sensor and comparison with a temperature table.